HEAT PRODUCTION OF HONEYBEES IN WINTER. 13 



cumulate in the air of the system in which there was a deficiency 

 of oxygen. The effect on the activity of the bees was soon apparent ; 

 the temperature curves, which for some reason had begun to rise, 

 very shortly turned in the opposite direction and continued to fall 

 for about 12 hours. The proportion of oxygen was then 12 per cent 

 and it was thought that the bees had probably been suffocated. Eight 

 hours before the time at which the period would regularly end the 

 air of the system was again put in circulation and water vapor and 

 carbon dioxid removed, oxygen being also removed at the same time. 

 This was continued until the close of the period (which was also 

 the end of the experiment) in order that the air of the system might 

 be quite thoroughly freed of carbon dioxid. After the circulation 

 of air was resumed the bees again indicated that they were living, 

 and during the time that the air-purifying system was operating 

 their activity increased until by the end of the experiment the tem- 

 perature curve had reached as high a point as at any time during 

 the course of the experiment, even though the proportion of oxygen 

 in the air was low. Analysis of the sample taken at the end of the 

 period showed only 7.3 per cent of oxygen. 



If the decrease in the activity of the bees in this instance was due 

 to atmospheric conditions in the hive, the cause was probably excess 

 of carbon dioxid and water vapor rather than deficiency of oxygen. 

 Though the proportion of oxygen in the air was decreased from 18 

 to 12 per cent in 16 hours, it is doubtful if this alone would have 

 an appreciable effect upon the physiological activity of the bees. In 

 experiments with men in atmospheres about as deficient in oxygen* as 

 this, there was no noticeable effect upon their metabolism. In these 

 experiments, however, there was no such excess of carbon dioxid and 

 water vapor as in the experiment with the bees. 



It is possible, as intimated on page 6, that the reason for the 

 increase in activity of the bees after the circulation of air was re- 

 sumed may have been physical disturbance. Since it was thought 

 that the bees were dying, movement about the laboratory was some- 

 what less restricted when the air-circulating device was started, al- 

 though care was still taken to avoid jarring the calorimeter. The 

 circulation of air through the calorimeter could hardly have caused 

 any disturbance of the bees, because the low rate, while sufficient to 

 keep the air in motion, could not produce any current that would stir 

 the hive. It is also possible that, since the removal of oxygen from 

 the air was continued during this period, the proportion of oxygen 

 in the air eventually became so low that the bees had to respire more 

 rapidly to obtain a sufficient quantity of this gas. It would be ex- 

 pected, however, that this effect would be manifested somewhat later 

 in the period than the time at which activity was renewed. 



